Rodless cylinder

Abstract

In a rodless cylinder comprising a series of driving magnets mounted on a piston fitted in a cylinder tube and a series of driven magnets on a driven member sliding along the cylinder tube, piping to convey a hydraulic fluid is simplified as follows. Both ends of the cylinder tube and guide rods extending parallel thereto are fastened to two end plates. Two ports through which the hydraulic fluid is supplied to and discharged from pressure chambers on both sides of the piston in the cylinder tube are provided in one of the end plates. While one of the ports communicates directly with one pressure chamber through the end plate, the other port communicates with the other pressure chamber through one of the guide rods and the other end plate. The driven member sliding along the cylinder tube carries the series of driven magnets and two annular sliding members on both sides thereof in such a manner as to be movable in the direction perpendicular to the axis of the cylinder. This eliminates the need of assembling the cylinder tube with very high accuracy. Also, the cylinder can exert its driving force to the maximum extent of its ability since any external force working on the driven member is supported by the guide rods.

What is claimed is: 
     
       1. A rodless cylinder which comprises: a cylinder tube whose both ends are fastened to end plates;   at least one guide rod disposed parallel to said cylinder tube, both ends of which being fastened to said end plates;   a piston carrying a series of driving magnets and slidably fitted in said cylinder tube;   a driven member sliding along said cylinder tube and carrying a series of driven magnets sliding along the peripheral surface of said cylinder tube, the series of driving and driven magnets attracting each other and the driven member having through-holes through which said guide rods are slidably passed;   one of said end plates having a pair of ports through which a hydraulic fluid is supplied to and discharged from pressure chambers on both sides of the piston in the cylinder tube, one of the ports communicating directly with one of the pressure chambers and the other port communicating with the other pressure chamber through one of the guide rods and passages provided in the other end plate.   
     
     
       2. A rodless cylinder according to claim 1 including two parallel ones of said at least one guide rod disposed on both sides of said cylinder tube, in which the end plates at both ends of the cylinder tube provide tight sealing thereto and firmly fasten the cylinder tube and the two parallel guide rods disposed on both sides thereof. 
     
     
       3. A rodless cylinder according to claim 2, in which the driven member sliding along the cylinder tube consists of a monolithic block having through-holes through which the cylinder tube and the two guide rods are passed. 
     
     
       4. A rodless cylinder according to claim 1, in which the piston fitted in the cylinder tube consists of a series of driving magnets which is made up of a plurality of alternately disposed annular driving magnets and yokes, the driving magnets and yokes being placed between a pair of piston members and assembled together with a bolt passed through holes in the driving magnets, yokes and piston members and a nut screwed thereon. 
     
     
       5. A rodless cylinder according to claim 4, in which the driven member sliding along the cylinder tube consists of a series of alternately disposed annular driven magnets and yokes fitted over the cylinder tube and placed between a pair of annular sliding members, the series of driving and driven magnets being disposed so that unlike poles thereof are positioned opposite to each other. 
     
     
       6. A rodless cylinder according to claim 1, in which a rail is provided between the end plates so that detectors to locate the position of the driven member are mounted in the desired position. 
     
     
       7. A rodless cylinder according to claim 2, in which adjust bolts to limit the stroke of the driven member are provided on the end plates. 
     
     
       8. A rodless cylinder which comprises: a cylinder tube whose both ends are fastened to end plates;   guide rods disposed parallel to said cylinder tube, both ends of which being fastened to said end plates;   a piston carrying a series of driving magnets and slidably fitted in said cylinder tube;   a driven member sliding along said cylinder tube;   a series of driven magnets carried by said driven member and sliding along the peripheral surface of said cylinder tube, the series of driven magnets attracting said series of driving magnets and being contained with a pair of annular sliding members disposed at both ends thereof, said driven member being moveable in the direction perpendicular to the axis of the cylinder relative to said annular sliding members and the driven member having through-holes through which said guide rods are slidably passed;   one of said end plates having a pair of ports through which a hydraulic fluid is supplied to and discharged from pressure chambers on both sides of the piston in the cylinder tube, one of the ports communicating directly with one of the pressure chambers and the other port communicating with the other pressure chamber through one of the guide rods and passages provided in the other end plate.   
     
     
       9. A rodless cylinder according to claim 8, in which the series of driven magnets and annular sliding members are contained in a holding cylinder of a nonmagnetic material, the holding cylinder being inserted, with spacers kept in contact with both ends thereof, in a bore provided in the driven member and fastened thnerein with stop rings engaging therewith, a small clearance being provided between said holding cylinder and said bore to thereby allow driven member to move in the direction perpendicular to the axis of the cylinder relative to said annular sliding members.